Render QImage with OpenGL

Question

Related to my other question, I think the more central question would be, how you render a QImage with OpenGL?

I think the code has to look something like t

Answer 1

I managed to draw a QImage with OpenGL from a picture source, but not from the SoOffscreenRenderer as described here.

void init(){
    loadTexture2("kitten.png", backgroundimage);
}

QImage loadTexture2(char *filename, GLuint &textureID){
    glEnable(GL_TEXTURE_2D); // Enable texturing

    glGenTextures(1, &textureID); // Obtain an id for the texture
    glBindTexture(GL_TEXTURE_2D, textureID); // Set as the current texture

    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

    QImage im(filename);
    QImage tex = QGLWidget::convertToGLFormat(im);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex.width(), tex.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, tex.bits());

    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);

    glDisable(GL_TEXTURE_2D);

    return tex;
}

void renderSceneGL2(){
    glClearColor(0.4f, 0.1f, 0.1f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, backgroundimage);

    glBegin(GL_QUADS);
        glTexCoord2f(0,0); glVertex3f(-1, -1, -1);
        glTexCoord2f(1,0); glVertex3f(1, -1, -1);
        glTexCoord2f(1,1); glVertex3f(1, 1, -1);
        glTexCoord2f(0,1); glVertex3f(-1, 1, -1);

    glEnd();

    glDisable(GL_TEXTURE_2D);
}

Also QGLWidget::convertToGLFormat throws random Access violation errors from time to time.